When driving screws with a power screw driver, it is generally difficult to determine the proper point at which to stop the driver to define the proper depth of the screw head with respect to the surface of the workpiece. Should the operator of the screwdriver stop too soon, the screw head will protrude from the surface of the workpiece. Consequently, the operator must attempt to advance the screw in small incremental distances until it reaches the desired proper depth. This is difficult to do and in many instances, not successfully achieved. On the other hand, should the operator stop too late, the screw head penetrates into the workpiece to a point below the surface thereof. This may result in damage to the assembly, or, in the case of dry wallboard for example, break the wallboard surface, thus reducing the strength thereof.
While devices currently exist which address the above-mentioned disadvantages, such devices usually rely on torque limiters which must be set prior to driving the screw as such devices cannot sense the location of a screw head in relation to the workpiece nor the torque required to properly seat the screw. Such torque widely varies not only with the material into which the screw is being driven, but with regard to the specific point at which the screw is driven.
There exists therefore, the need for a device to limit the screw head depth which does not exhibit the disadvantages of the above-mentioned devices. The present invention fulfills such a need.